1. Field of the Invention
The present invention is related to a photography apparatus and a photography method that perform a plurality of photography operations under different photography conditions, then processes the image signals obtained by the photography signals to obtain various image signals.
2. Description of the Related Art
CCD's, which are imaging means employed in digital cameras, have narrower dynamic ranges than silver salt film. Therefore, overexposure and underexposure are likely to occur in images photographed by digital cameras. For this reason, there are known techniques for obtaining image signals having expanded dynamic ranges that exhibit favorably reproduction properties over a wide range from high brightness to low brightness. In these techniques, imaging is performed with different exposure conditions to obtain an image signal that represents an image having a large amount of data toward the high brightness side, and an image signal that represents a image having a large amount of data toward the low brightness side, for example, and then the image signals are combined to obtain an expanded dynamic range image signal.
Examples of techniques for obtaining image signals having expended dynamic ranges based on a plurality of image signals are disclosed in U.S. Pat. No. 6,753,920, and Japanese Unexamined Patent Nos. 2006-148591 and 2008-016862.
Generally, in the case that the aforementioned techniques are employed to obtain a dynamic range expanded image data set having a dynamic range which is expanded n times that of an image obtained by standard photography, an image data set, which is photographed with the same amount of exposure as that during standard photography, and an image data set, which is photographed with an exposure amount 1/n times that during standard photography, are required. In the case that the dynamic range is to be expanded to 800% (8 times), for example, an image data set, which is photographed with the same amount of exposure as that during standard photography, and an image data set, which is photographed with an exposure amount ⅛ that during standard photography, are required. That is, it is necessary to decrease the exposure amount compared to that during standard photography, in order to greatly expand the dynamic range.
In the case that the aforementioned techniques are applied to image signals which are obtained while flash is emitted, an image signal obtained by photography with an exposure amount equivalent to that of standard photography with standard flash emission and an image signal obtained by photography with an exposure amount 1/n times that of standard photography with the amount of flash emission suppressed to 1/n become necessary.
However, it is difficult to accurately control the amount of emitted flash along to match set exposure ratios. In a technique that controls the amount of flash emission by changing the amount of flash emission time as disclosed in U.S. Pat. No. 6,753,920, fluctuations in the amount of flash emission occur, and dynamic range expanding processes cannot be performed accurately.
Meanwhile, Japanese Unexamined Patent Publication Nos. 2006-148591 and 2008-016862 are silent regarding control of flash during flash emission.
Further, processes in which a single image signal is generated based on a plurality of image signals is not limited to the dynamic range expanding process. There are various such types of image processes, such as a multi frame process, in which an image having a shallow subject field depth or an image having a deep subject field depth is generated from image signals that represent a plurality of frames. The same problems regarding flash emission apply to these processes as well.